In U.S. Pat. No. 8,685,156 (owned by W. R. Grace & Co.-Conn.), Koyata et al. disclosed that the use of polycationic compounds in combination with hydroxycarboxylic compounds enhanced slump retention in concretes having clay-bearing aggregates, in which the clay otherwise absorbs or diminishes the dosage efficiency of the polycarboxylate superplasticizers.
In US Patent Publication No. US 2014/0323614 A1 (owned by Lafarge), Villard et al. disclosed a mixture for treating concrete which included an inerting agent for at least partially neutralizing harmful effects of impurities on the workability of the concrete, a first superplasticizer that was different from the inerting agent, and a second superplasticizer that was different from the first super-plasticizer and the inerting agent. The two superplasticizers taught by Villard et al. differed in that one of the superplasticizers had a maximum plasticizing action developing after the peak of the plasticizing action of the other superplasticizer.
The present inventors believe that a novel and inventive super-plasticizing admixture for modifying concrete, particularly when clay contaminants are present, is needed.